a. Field of Invention
The invention relates generally to an expanding shaft, and, more particularly to an expanding shaft of the type which carries tubular supports on which strips of plastic, aluminum or paper films are wound or from which the strips are unwound.
b. Description of Related Art
During the manufacture of plastic, aluminum, paper or other sheet products, the sheet material is typically wound onto, or unwound from, a tubular core supported by a diametrically expansible shaft which is inserted into the core and expanded to grip the core frictionally. Such shafts are typically used when slitting a wide web of material into discrete widths and rewinding the material on the core. Conventional expansible roll core shafts typically employ a large number of relatively small, separate core-engaging elements expansible by a common internal air-expandable bladder, or by a plurality of individually controllable air-expandable bladders.
Of known varieties of expansible shafts, as disclosed in U.S. Pat. No. 3,904,144, the disclosure of which is incorporated herein by reference, one type of shaft includes straight, parallel slots cut longitudinally in the periphery thereof. The slots include straight, separate, air-expandable, resilient bladders overlain by respective straight core-contacting elements which extend throughout the length of the shaft. One key drawback in such a shaft is in the overall ability to evenly load delicate cores to eliminate core distortion or damage, and the overall excessive weight of such shafts, which requires the implementation of special handling procedures and methods, and thus increases the overall manufacturing and operational costs for such shafts.
Other known varieties of expansible shafts include the shaft designs disclosed in U.S. Pat. Nos. 5,597,134 and 5,746,386, the respective disclosures of which are incorporated herein by reference.
The expansible shafts disclosed in the '134 and '386 patents disclose the use of mobile means mounted for radial movement within slots in the expanding shaft. Core stops are adjustably mounted for axial movement longitudinally of at least one of the mobile means to vary the spacing of the core stops longitudinally of the shaft as desired. Locking means is provided for locking the core stops in position axially of the mobile means and the shaft. With the arrangement as shown in the '134 and '386 patents, the longitudinal position of the core stops relative to the shaft can be adjusted while the shaft is mounted on a slitter-rewinder machine. However, due to the weight of the shaft and associated components, it generally takes a significant amount of labor and down time of the machine while such changes are made.
While the expansible shaft disclosed in U.S. Pat. No. 6,196,494, which is owned by the assignee herein and the disclosure of which is incorporated herein by reference, provided significant improvement in the construction of an expansible shaft over the shafts disclosed in the '134 and '386 patents so as to permit the slit widths on a slitter-rewinder machine to be changed in a minimum amount of time, there remains a need for an improved expansible shaft having a reduced overall weight for further facilitating the overall manufacturing and operational costs thereof. There also remains a need for an improved expansible shaft which enables the application of higher torsional loads, and improved core loading for eliminating core distortion or damage, and an expansible shaft which is easier to assemble and disassemble, which includes a limited number of required components for ease of operability as well as for increased reliability and robustness of design, and which is economically feasible to manufacture.